VIPA CP 240 RS232, Manual

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Manual VIPA System 200V Chapter 4 CP 240 - serial
HB97E - CP - Rev. 11/30 4-13
3964R appends a B lock c heck c haracter to safeguard the transmitted
data. The BCC-Byte is calculated by means of an XOR function over the
entire data of the message, including the DLE/ETX.
When a BCC-Byte is received that differs from the calculated BCC, a NAK
is transmitted instead of the DLE.
If two stations should simultaneously attempt to issue a connection request
within the QVZ then the station with the lower priority will transmit the DLE
and change to receive mode.
The driver duplicates any DLE-character that is contained in a message,
i.e. the sequence DLE/DLE is sent. During the reception, the duplicated
DLEs are saved as a single DLE in the buffer. The message always
terminates with the sequence DLE/ETX/BCC (only for 3964R).
The control codes : 02h = STX
03h = ETX
10h = DLE
15h = NAK
When ZVZ expires during the reception, the driver will send a NAK and
wait for another connection request.
The driver also sends a NAK when it receives an STX while it is not ready.
SEND (transmission of data )
Active partner
Passive partner
Message data
Reactions message
Next message
Next reaction message
etc.
When the data quantity > 128 bytes
subsequent messages are,
transmitted until all the data has
been transferre.
FETCH (retrieving data)
Next m data
in case of error only reaction message
Active partner Passive partner
Message header
Next message
etc.
Reaction m data
in case of error only reaction message
When the data quantity > 128 bytes
subsequent messages are
transmitted until all the data
has been transferred.
In both cases the procedures will time out after a maximum period of 5s
during which a reaction must be received, else the reception is terminated.
Block check
character
(BCC-Byte)
Initialization
conflict
Data Link Escape
(DLE-character)
Logical message
sequence